Power unit for vehicle

Abstract

A speed reducing gear train includes a starter driven gear, a starting one-way clutch interposed between the starter driven gear and a crankshaft for permitting power transmission from the starter driven gear to the side of the crankshaft. The speed reducing gear train and the starting one-way clutch being provided between a starter motor and the crankshaft with a transmission accommodated in a crankcase. The transmission includes gear trains for selectively establishing a plurality of gear speeds with the gear trains being between a main shaft and a counter shaft. The starter motor can produce power for driving the vehicle and to impart a drive assisting force. A power transmitting gear meshing with the starter driven gear is relatively rotatably mounted on the main shaft through a running one-way clutch permitting power transmission from the power transmitting gear to the side of the main shaft.

What is claimed is: 
     
       1. A vehicle power unit comprising:
 a speed reducing gear train including a starter driven gear selectively rotatably mounted on a crankshaft, said crankshaft being rotatably mounted on a crankcase constituting part of an engine body; 
 a starting one-way clutch interposed between the starter driven gear and the crankshaft so as to permit power transmission from the starter driven gear to the side of the crankshaft, the speed reducing gear train and the starting one-way clutch being provided between a starter motor mounted to the engine body and the crankshaft; 
 a transmission accommodated in the crankcase, the transmission having gear trains for a plurality of gear speeds which can be selectively established, the gear trains being provided between a main shaft and a counter shaft which have axes parallel to the crankshaft; and 
 
       a power transmitting gear meshing with the starter driven gear is selectively rotatably mounted on the main shaft through a running one-way clutch to transmit rotation from the power transmitting gear to the main shaft,
 wherein the starter driven gear includes a rotary member selectively rotatably mounted on the crankshaft through the starting one-way clutch interposed between the rotary member and the crankshaft, a gear member selectively rotatably mounted on the crankshaft and meshing with the power transmitting gear and a shifter mounted on the rotary member to be axially movable in a direction along the axis of the crankshaft and to be incapable of rotation, said shifter including a dog selectively engagable and disengagable with the gear member. 
 
     
     
       2. The vehicle power unit according to  claim 1 , wherein a power transmission change-over mechanism for change-over between power transmission from the crankshaft to the main shaft and cutoff of the power transmission is provided between the crankshaft and the main shaft. 
     
     
       3. The vehicle power unit according to  claim 1 , wherein the speed reducing gear train includes a starter drive gear operatively mounted on an output shaft of the starter motor, a first idle gear meshing with the starter drive gear, a second idle gear formed integrally with the first idle gear and the starter driven gear meshing with the second idle gear. 
     
     
       4. The vehicle power unit according to  claim 3 , and further including a support shaft for operatively mounting the first and second idle gears, formed as one body, wherein one end portion of the support shaft is supported by the crankcase and the other end portion of the support shaft is supported by a crankcase cover. 
     
     
       5. The vehicle power unit according to  claim 1 , wherein the gear member is operatively mounted on the crankshaft between one end of the rotary member and a case half of the crankcase with the other end of the rotary member abutting a rotor of a generator. 
     
     
       6. The vehicle power unit according to  claim 5 , wherein the case half of the crankshaft is integrally provided with an annular projecting portion extending towards the gear member for clamping the rotary member and the gear member between the annular projecting portion and the rotor. 
     
     
       7. The vehicle power unit according to  claim 1 , wherein the shifter includes a shift fork fixed to a shifter shaft mounted on an axis extending parallel to the main shaft, one end portion of the shifter shaft being axially slidably fitted in a support tube portion provided on a case half of the crankcase, a third crankcase cover is provided with a support aperture through which the shifter shaft is slidably passed with an annular seal being interposed between the third crankcase cover and the shifter shaft. 
     
     
       8. A vehicle power unit comprising:
 a speed reducing gear train including a starter driven gear relatively rotatably borne on a crankshaft, said crankshaft being rotatably mounted relative to a crankcase; 
 a starting one-way clutch interposed between the starter driven gear and the crankshaft for permitting power transmission from the starter driven gear to the side of the crankshaft, said speed reducing gear train and the starting one-way clutch being provided between a starter motor and the crankshaft; 
 a transmission accommodated in the crankcase, said transmission having gear trains for a plurality of gear speeds which can be selectively established, the gear trains being provided between a main shaft and a counter shaft which have axes parallel to the crankshaft; 
 a power transmitting gear meshing with the starter driven gear is selectively rotatably mounted on the main shaft through a running one-way clutch to transmit rotation from the power transmitting gear to the main shaft; and 
 said starter driven gear includes a rotary member selectively rotatably mounted on the crankshaft through the starting one-way clutch interposed between the rotary member and the crankshaft, a gear member selectively rotatably mounted on the crankshaft and meshing with the power transmitting gear, and a shifter mounted on the rotary member to be axially movement in a direction along the axis of the crankshaft and to be incapable of rotation, said shifter including a dog selectively engagable and disengageable with the gear member. 
 
     
     
       9. The vehicle power unit according to  claim 8 , wherein a power transmission change-over mechanism for change-over between power transmission from the crankshaft to the main shaft and cutoff of the power transmission is provided between the crankshaft and the main shaft. 
     
     
       10. The vehicle power unit according to  claim 8 , wherein the speed reducing gear train includes a starter drive gear operatively mounted on an output shaft of the starter motor, a first idle gear meshing with the starter drive gear, a second idle gear formed integrally with the first idle gear and the starter driven gear meshing with the second idle gear. 
     
     
       11. The vehicle power unit according to  claim 10 , and further including a support shaft for operatively mounting the first and second idle gears, formed as one body, wherein one end portion of the support shaft is supported by the crankcase and the other end portion of the support shaft is supported by a crankcase cover. 
     
     
       12. The vehicle power unit according to  claim 8 , wherein the gear member is operatively mounted on the crankshaft between one end of the rotary member and a case half of the crankcase with the other end of the rotary member abutting a rotor of a generator. 
     
     
       13. The vehicle power unit according to  claim 12 , wherein the case half of the crankshaft is integrally provided with an annular projecting portion extending towards the gear member for clamping the rotary member and the gear member between the annular projecting portion and the rotor. 
     
     
       14. The vehicle power unit according to  claim 8 , wherein the shifter includes a shift fork fixed to a shifter shaft mounted on an axis extending parallel to the main shaft, one end portion of the shifter shaft being axially slidably fitted in a support tube portion provided on a case half of the crankcase, a third crankcase cover is provided with a support aperture through which the shifter shaft is slidably passed with an annular seal being interposed between the third crankcase cover and the shifter shaft.